Thanksgiving travelers, beware: flying or driving to reunite with far-flung friends and family could be an absolute nightmare.

A storm that’s already been blamed for at least 12 deaths and hundreds of car crashes across the western and southern U.S. is now headed for the East Coast. As the system tracks eastward, it’s expected to dump inches of rain, snow and sleet from New England down to the Carolinas, according to the Associated Press.

Exactly how badly you’ll get hit depends on where you are: the coastal areas will see rain or freezing rain, while inland and elevated areas will get sleet and snow. “The further inland you get — especially as you get into that higher terrain — you are going to deal with frozen precipitation,” AccuWeather meteorologist Tom Kines told AP.

Freezing rain and snow will force many East Coast airports to delay or outright cancel flights, sending ripple effects through the entire air-transit system. Likewise, slick surfaces and low visibility will make roads hazardous for drivers on one of the busiest commuting days of the year. While AAA expects a 1.6% decrease in the number of people driving this Thanksgiving season, 38.9 million Americans will still find themselves on the road some time this week.

The combination of bad weather and crowded highways is a recipe for accidents and delays, so take caution if you’re still determined to move about the East Coast this Thanksgiving.